1. Field of the Invention
The present invention relates to a vibrating gyroscope preferably for use as an angular velocity detecting sensor. More particularly, the present invention relates to a vibrating gyroscope including a frame body in which a first vibrating portion and a second vibrating portion are provided.
2. Description of the Related Art
An angular velocity detecting sensor for detecting the position of a moving body has been widely used. An example of such an angular velocity detecting sensor is disclosed in Japanese Unexamined Patent Application Publication No. 8-278146 and shown in FIGS. 13A and 13B.
FIG. 13A is a perspective view of a known vibrating gyroscope 1001. FIG. 13B is a sectional view taken along line B-B in FIG. 13A. The vibrating gyroscope 1001 includes a vibrating body 1002 having a rectangular frame shape. In the vibrating body 1002, a pair of vibrating portions 1002a and 1002b extending in a direction of a long side of the rectangular shape are coupled to each other by a pair of coupling portions 1002c and 1002d extending in a direction of a short side of the rectangular shape.
A driving piezoelectric element 1003 and a driving piezoelectric element 1004 are secured to a top surface of the vibrating portion 1002a and a top surface of the vibrating portion 1002b, respectively. A detecting piezoelectric element 1005 and a detecting piezoelectric element 1006 are provided on an outer side surface of the vibrating portion 1002a and an outer side surface of the vibrating portion 1002b, respectively.
In the vibrating gyroscope 1001, an oscillation circuit is connected to the driving piezoelectric elements 1003 and 1004, so as to vibrate the vibrating portions 1002a and 1002b. That is, the entire vibrating body 1002 having a rectangular frame shape vibrates in a buckling tuning-fork vibration mode.
When the vibrating gyroscope 1001 is subjected to angular velocity while the vibrating body 1002 is vibrated, the vibration mode changes. An output voltage between the detecting piezoelectric elements 1005 and 1006 makes it possible to detect angular velocity of rotation based on the change in the vibration mode.
In Japanese Unexamined Patent Application Publication No. 8-278146, since nodes are positioned near respective ends of a diagonal of the vibrating body 1002 having the rectangular frame shape, the vibrating body 1002 can be supported near the respective ends of the diagonal. Consequently, it is possible to simplify a supporting structure.
In the vibrating gyroscope 1001 discussed in Japanese Unexamined Patent Application Publication No. 8-278146, the vibrating portions 1002a and 1002b undergo bending vibration. Therefore, the entire vibrating body 1002 vibrates in a buckling tuning-fork vibration mode. When such a vibrating gyroscope 1001 is reduced in size, its detection sensitivity is reduced.
When further reducing the size of the vibrating gyroscope 1001, it becomes difficult to achieve stable precision of the sizes and shapes of structural members of the vibrating gyroscope, as a result of which sensitivity changes.